1. Field of the Invention
The present invention relates to a method for operating a memory, and more particularly to a method for operating a one-time programmable read-only memory (OTP-ROM).
2. Description of Related Art
As functions of microprocessors continue to be expanded, an amount of computation in a given software program increases exponentially, and demands for memories are also increasing. As a result, it is an essential issue for semiconductor manufacturers to satisfy said demands by fabricating the inexpensive memories with great storage capacity. According to differences in read/write functions, the memories can be simply categorized into read-only memories (ROMs) and random access memories (RAMs). As the name suggests, the ROMs merely perform the read function, while the RAMs are equipped with both the read function and the write function. On the other hand, the ROMs can be classified into mask ROMs, programmable ROMs (PROMs), erasable programmable ROMs (EPROMs), and electrically erasable programmable ROMs (EEPROMs) based on a way by which data are stored in the memories. RAMs can be divided into static RAMs (SRAMs) and dynamic RAMs (DRAMs) according to a way by which the data are processed in the memories.
Recently, among various integrated circuit (IC) devices in the semiconductor industry, OTP-ROMs characterized in that the data stored therein do not disappear even though the power is low have become indispensable. The OTP-ROMs may be extensively applied to perform a redundant function in the memories having great storage capacity, such as the DRAMs or the SRAMs. Besides, the OTP-ROMs may also be utilized for performing a calibrating function for analog circuits, a code storage function for low keys, a data storage chip identification (ID) function for managing a fabrication process, and so forth.